Folding knife



FIG. 1 is a left side view in elevation of the ornamental design of a folding knife, the broken lines are for illustrative purposes only and are not part of the claimed design;

FIG. 2 is a top plan view of the folding knife shown in FIG. 1;

FIG. 3 is a right side view in elevation of the folding knife shown in FIG. 1;

FIG. 4 is a bottom plan view of the folding knife shown in FIG. 1;

FIG. 5 is a front plan view of the folding knife shown in FIG. 1;

FIG. 6 is a rear plan view of the folding knife shown in FIG. 1;

FIG. 7 is a perspective view of an enlarged fragmentary portion of the textured grip of the folding knife as seen in FIGS. 1 and 3; and,

FIG. 8 is a view in elevation taken on line 8--8 of FIG. 7 for clarity. 

The ornamental design for a folding knife, as shown and described. 